Radio frequency store and display system

ABSTRACT

The binary coded signals actuating the digital frequency indicator, indicating the radio frequency to which a communication set is tuned, are transferred to a second digital frequency indicator upon the manual actuation of a momentary push button switch. The second digital indicator system stores and continuously displays the former frequency irrespective of any subsequent tuning of the communication set until the momentary switch is again activated to store and display the frequency to which the communication set is then tuned.

United States Patent Ravenelle et al.

[451 Nov, 27, 1973 Primary Examiner-Albert J. Mayer Attorneyl-larry A. Herbert, Jr. et al.

[ 5 7 ABSTRACT The binary coded signals actuating the digital frequency indicator, indicating the radio frequency to which a communication set is tuned, are transferred to a second digital frequency indicator upon the manual actuation of a momentary push button switch. The second digital indicator system stores and continuously displays the former frequency irrespective of any subsequent tuning of the communication set until the momentary switch is again activated to store and display the frequency to which the communication set is then tuned.

1 Claim, 11 Drawing Figures RADIO FREQUENCY STORE AND DISPLAY SYSTEM [75] Inventors: Richard L. Ravenelle; David E.

Thorburn, both of Dayton, Ohio [73] Assignee: The United States of America as represented by the Secretary of the Air Force [22] Filed: July 6, 1972 [21] Appl. No.: 269,358

[52] US. Cl. 325/455, 325/25 [51] int. Cl. H04b 1/06 [58] Field of Search 325/25, 455, 53

[56] References Cited UNITED STATES PATENTS 3,701,945 10/1972 Gallant 325/25 3,281,789 10/1966 Willcox et al.. 3,244,983 4/1966 Ertman 325/455 M 0M 67V 7- 495/ M q 5 u r'ro N I 8 g PATENTH] NUV 2 7 I973 5 Z Z Z5.

Ava/car p PATENIEI] HHV 2 71973 SHEET 8 OF 6 26 erwu m RADIO FREQUENCY STORE AND DISPLAY SYSTEM BACKGROUND OF THE INVENTION The field of the invention is in the radio communication art.

A problem which adds to cockpit workload is the requirement for the aircrew to keep track of the last working radio frequency to insure against lost communications. For example, a specific working frequency may be established for command communications for one particular area or zone, with ancillary communications taking place on different frequencies. In such instances the primary frequency is departed from to briefly monitor or communicate on other frequencies with the necessity often arising to rapidly return to the basic assigned communicating frequency. Departing from a tower frequency to communicate on another frequency with another aircraft is an example of shifting from a primary frequency. A typical military example illustrating the worst-case situaton is that of the pilot of a single seat fighter aircraft leading a flight in bad weather, in a combat area where radio saturation prevails. In this instance the simple act of recalling a radio frequency can become most demanding. A less critical problem in radio-frequency changing occurs in multi-crew aircraft when a second crew member is available to record assigned radio frequencies. However, from a practical viewpoint, the fact that many pilots write down a newly assigned frequency before acknowledging the radio call represents an appreciable slow down in the communication process which often becomes serious under conditions of high traffic density. When it is understood that the assigned frequency for a specific purpose usually changes from area to area, and operation to operation, and that hundreds of frequencies are available, the act of recalling under stress a specific frequency, even with a pad full of grease pencil frequency scribblings approaches the insurmountable, and quite frequently resort must be had to using the guard (emergency) frequency to reestablish radio contact. This is very detrimental to rapid and efficient communication. The radio communication frequencies are indicated in megahertz over the particular communication band for which the set was designed. A typical range for a communication band being the UHF range from 225.0 to 399.9 megahertz. This range is normally divided into channels and the tuning is thus in step increments. Many widely used communication sets divide this range into 100 kHz steps thus providing 1,750 channels of communication. Some more complex sets divide the range into 50 kHz steps thus providing 3,500 separate communication channels in this particular band. A particular assigned frequency would be anywhere in this range, such as 341.1, which would be the reference frequency to which to return after communicating on another frequency or after manually tuning (switching) to other frequencies to monitor for possible communications. Some communication sets have available as many as twenty preset frequency buttons whereby a particular frequency, or frequencies, may be set during the preflight planning stage prior to takeoff. The preset frequencies may then be selected during flight by pushing a preset button. These preset frequency selectors are advantageous when the pilot previously knows a particular frequency that is used in an area through which he contemplates flight, however it is generally recognized that in most missions that the majority of the assigned communicating frequencies used during the course of the mission will be assigned in flight and not known until just prior to their actual usage, i.e., when directed to change from a present command frequency to a new command frequency. Generally, it is not attempted to set the presets during flight. Thus, the need of knowing a particular frequency and the utility of this invention is just as great with communication sets having preset frequency buttons as with sets without presets.

An obvious solution to the foregoing problem is to have more than one communication set and leave one set tuned to an assigned frequency while another set is used to tune to other frequencies. Equally as obvious is the fact that in many situations, such as fighter aircraft, where space and weight are at a premium, and many other pieces of electronic equipment are required, that the complexity of adding even one more communication set is prohibitive. This invention is equally applicable to light private aircraft, especially in single pilot, single radio cases.

SUMMARY OF THE INVENTION By pushing a momentary electrical push button switch the indicated radio frequency to which a communication set is tuned is electrically transferred to, and stored by, a separate visually indicating frequency indicator that retains and displays the stored frequency so that the operator, after tuning to other frequencies, will have indicated before him the frequency of the former transmission, to which he may readily retune, without the need for memorizing or writing down the former frequency. The invention thus speeds up radio frequency changes and reduces errors in changing frequencies which greatly reduces the pilot and air traffic controller workload thus promoting air safety and efficient communications.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a simplified pictorial view of an embodiment of the invention having a separate store-recall panel;

FIG. 2 is a simplified pictorial view showing an embodiment of the invention in which the store and recall indication is contained in the radio control panel.

FIG. 3 is a simplified overall block diagram of a radio communication system having a store and recall frequency indicator;

FIG. 4 is a simplified block diagram showing multiple store and recall indicators;

FIG. 5 is a pictorial view of a typical single seat fighter airplane cockpit showing a typical installation of the invention;

FIG. 6 is an enlarged pictorial view of the radio instrument panel shown in FIG. 5;

FIG. 7 is a typical connection diagram showing the modification in the wiring of a typical communication set to incorporate the improvement of the invention;

FIG. 8 is a schematic diagram of the circuitry cooperation with the wiring diagram of FIG. 7 for a typical embodiment of the invention having an electromechanical readout store recall indicator;

FIG. 9 is a block-schematic diagram of a typical embodiment of the invention using solid state electronic circuitry with light emitting diode display indication; and

FIGS. and 10a are logic diagrams ofa typical code converter.

DESCRIPTION OF THE PREFERRED EMBODIMENT The novel store and recall system as disclosed herein for indicating a selected frequency may be either added to the conventional communication radio set as a separate unit as shown in FIG. I or incorporated in the communication set control panel as shown in FIG. 2. The radio control panel 11, FIG. 1, and 21 FIG. 2 may be either a remote control of the communication set or integral with the set. In a typical embodiment of the invention the communication set tunes (in channelized steps) the communication band of approximately 225.0 megahertz to 399.9 megahertz. Tuning the tuning knobs 12, FIG. 1, and 22, FIG. 2, selects the transmitting and receiving frequency which is displayed numerically at 13, FIG. 1, and 23, FIG. 2. When the momentary push button 14 in the separate indicating panel 15 is actuated the frequency to which the communication set is then tuned as indicated 13, is then displayed 16 on the recall indicator. This numerical indication remains displayed in the store recall indicator until the push button 14 is again pushed, at which time the frequency indication in the store recall indicator will change to the frequency to which the set is then tuned. The embodiment shown in FIG. 2 functions in the same manner except the momentary store push button 24 and the displayed stored frequency 25 are both contained in the radio control panel. FIG. 2 symbolizes a communication set tuned to 3 I 8.9 megahertz, and the frequency which is stored for future reference is 34l.l megahertz. If the store button 24 were pushed at this time the stored frequency 341.1 indicated 25 would change to the tuned frequency 318.9. The store push button may be either located in a remote store recall indicator as shown in FIG. 1 or the recall indicator may be remote from the control panel with the store button located on the main control panel.

The embodiments shown in FIGS. 1 and 2 are particularly suitable for one-man aircraft. In multi-crew aircraft the communication set (transmitter and receiver) usually controlled from more than one control box. FIG. 3 is a typical simplified block diagram of such an installation. The primary control box 31 may be located either for the pilot, copilot, navigator, or radioman with secondary control boxes located for each of the other enumerated positions. Generally, a store recall indicator will be located with or in each control box. In some installations it is desirable to slave a second, or more, recall indicators actuated by a common store button 32. Another type of installation particularly suited for the radioman of large aircraft is shown in FIG. 4. By the use ofmultiple store and recall indicator systems two or more frequencies may be stored and indicated for instant recall. With more and more congestion occurring in the communication spectrum and with faster aircraft and tighter scheduling of flights, any time saved in the communication process is a great safety factor. With installations as shown in FIG. 4 the rarioman, at the push of a button, has before him for future reference a recorded frequency, which is greatly more expedient and accurate than writing the frequency down on a pad of paper. This is particularly true when the plane is maneuvering and legible writing may be very difficult. FIG. 5 is an outline sketch of a cockpit of a typical single seat fighter aircraft showing a typical location 51 of the radio control panel. A typical location for a separate store recall indicator system such as shown in FIG. 1 would be in panel 52. Embodiments of the invention having electrical indicating recall indication, such as light emitting diodes, may frequently be installed adjacent the conventional radio control panel in the original panel space 51. FIG. 6 is a view of an example of a conventional type AN/ARC -34 radio set control panel with the added store recall indicator panel 62. The store button 63 activates the recall indication to that of the tuned frequency. The electrical recall indication may be made with conventional seven element character displays as shown or any of the many other well known display character types. In the electrically displayed embodiments the type of element providing the display may be conventional light emitting diodes, incandescent filaments, nixie tubes, or any of the other well known electrical indicators.

In one particular embodiment, in which the invention was combined with a conventional AN/ARC-34 radio set, the modification in the conventional wiring to include the invention was made as shown in FIG. 7. The conventional control box is a type C-l057B/(ARC- 34) actuating a conventional frequency indicator 77, which in this particular instance is a type ID-573/ARC. This type indicator is constructed so that additional indicators may be slaved, in series relationship, from previous indicators. Thus, for a conventional system having two indicators, 77 and 78, both tracking the tuning and indicating the tuned frequency, wire 73 would not be broken, i.e., terminals 71 and 72 would not be inserted in the line, and indicator 78 would be slaved to indicator 77. To incorporate the invention in this particular system line 73 is broken and terminals 71 and 72 are provided and a tapped terminal 74 is made on the ground line. Indicator 78 with the inclusion of the circuitry of FIG. 8 now becomes a recall indicator to provide an embodiment of the invention such as shown in FIG. 3. Conventional frequency indicator 77 functions in the normal manner tracking the tuned frequency. To provide additional recall indicators, as indicated 33 in FIG. 3, slaved to the first recall indicator 34, connections are made in the conventional manner to terminals indicated 75 in FIG. 7. The recall indicator 34 than becomes the master control for the next recall indicator with as many recall indicators in series relationship as desired, all actuated from the single store button 32.

It is highly desirable that only a momentary actuation of store push button be required of the pilot or operator without any time limit requirements being placed on the holding down of the button. The conventional electro-mechanical indicator unit, such as the type ID- 573/ARC has a maximum response time of slightly less than l.2 seconds, i.e., it requires slightly less than 1.2 seconds to completely change indication from 225.0 to 399.9, thus for this type indicator connection from terminal 71 to terminal 72 must be maintained for approximately this length of time so that the recall indicator can change to the tuned indication. For purposes of this invention the requirement is that the circuitry actuated by the store button have such a time constant as to maintain energy (i.e., closed connection between terminals 71 and 72) to the particular recall indicator being used such that recall indicator can completely change indication over the tuning range of the particular communication set to which it is applied in the worst (longest time requirement) case.

The electronic circuit as shown in FIG. 8 when connected to the wiring as shown in FIG. 7 (Le, terminals 71, 72, and 74 of the two figures connected together, respectively), will provide operation as follows. Momentary actuation (closing) of the normally open store push button 81 charges the capacitor 82 to the standard 27.5 volt dc airplane power potential. Capacitor 82 charges practically instantaneously due to the RC time constant of capacitor 82 and resistance 83 being very small and the potential source impedance being quite low, thus, push button 81 does not have to be held down for any noticeable length of time. The positive potential on capacitor 82 through resistance 84 is placed on the base of transistor 85 placing it in emitter-base conduction energizing relay 86 and closing the normally open relay contacts 87. This energizes the drive mechanism in the electro-mechanical recall indicator 78 (FIG. 7) which in the particular embodi-,

ment being described is another conventional indicator such as type ID-573/ARC. The relay 86 stays closed by current conduction through the transistor 85 until the charge potential on capacitor 82 drops the base of the transistor 85 to that potential at which the current conduction through the transistor is no longer great enough to provide the current required through the relay 86 to keep it closed. This time interval in which the relay will remain closed is a function of the RC time constant involving the capacitor 82, the resistance 84, and the base-emitter resistance characteristic of the transistor, considered with the emitter-collector current characteristic of the transistor and the operating current characteristics of the relay. The calculation of these design characteristics are well known in the art. The requirement, as previously stated, is that the relay remain closed long enough to provide the time interval necessary for the recall indicator to change numerical indication in the worst condition (i.e., the numerical change of indicated frequencies requiring the maximum time interval). For the conventional ID-573/ARC unit, 1.2 seconds has been found to be satisfactory. It is understood that the actual physical values of components used will vary with respect to the relationship with other components used and the particular equipment to which this invention is applied. Diodes 88 and 89 prevent any inductive reactance effects that may be present from affecting the operation of the circuit. In some installations they may not be required.

The wiring diagram shown in FIG. 7 shows the recall indicator 78 connected to a conventional frequency indicator 77. This is also shown by the solid line connections of FIG. 3. In some installations where it is desirable not to have a separate frequency indicator 77, the store recall system may be connected directly to the control box. Thus, in FIG. 7 cable 76 would connect to plug 79 connected with the jack of the control box 70 and indicator 77 would be omitted. This is also represented by the dotted line 35 of FIG. 3.

The modern trend is moving in the direction of all solid state readout devices. FIG. 9 shows a typical block schematic circuit of the embodiment of the in- 'vention using seven elements LED (light emitting diodes) for the numerical indication. The binary coded signals used with frequency indicating devices for many of the modern communication sets are the standard BCD (Binary-Coded Decimal) input signals using positive logic compatible with conventional TTL and DTL families. (For a typical example, the logic 0 input is at zero volts with respect to the network ground potential, with a maximum permissible deviation of +0.8 volts, and the logic 1 input is at a nominal 3-volt potential with a 2.0 volt minimum requirement and 6.0 volt limit requirement, all with respect to the network ground terminal.) When this invention is used with communication sets having the conventional BCD coded information signals on the indicator control lines of cable 91 the code converters 101, 102, 103, and 104 are not needed and the signal lines feed directly into the storage units. A typical truth table of the conventional code is as follows.

Display digit Indicator control line a 0 1 0 1 0 1 0 1 0 1 Indicator control line b. 0 0 1 1 0 0 1 1 0 0 Indicator control line 0 0 0 0 0 1 1 1 1 0 0 Indicator control line (1 0 0 0 O 0 0 0 0 1 1 Display digit Indicator control line a 0 Indicator control line b x Indicator control line 0 Indicator control line (1 0 Thus, when using conventional solid state BCD systems with this model of the AN/ARC-34 communication set code converters as shown 101, 102, 103, and 104 must be used. Code converters are well known and are readily available for converting signals of one code to another. An example of a code converter using conventional AND and OR gates and signal inverters is shown in FIGS. 10 and 10a. This converter will convert the previously shown code for the AN/ARC-34 to the conventional BCD code. A separate code converter is required for each display digit as shown in FIG. 9. It is to be understood that in instances where the coded signals from the communication set are not the standard BCD signal that an appropriate code converter will be used to convert the non-standard code into the conventional system. A typical embodiment using conventional solidstate storage and decoder driver modules actuating a conventional seven element LED display constructed to cooperate with conventional aircraft 27.5 volt power potential is shown in FIG. 9. Cable 91 connects to the conventional aircraft radio control box or a conventional frequency indicator as shown and 77 in FIG. 7. The particular solid state modules used in one embodiment are designed to operate from a 5 volt power source. (Examples of particular modules that have been found suitable are type MQL 105 storage units, type MSD 047 decoder driver units, and type MDA 100 display units.) Since the primary aircraft power is 27.5 volts this voltage is reduced by the transistor 92, resistor 93 and zoner diode Q4 to provide the 5 volts at approximately one ampere requirement of this particu lar solid state circuitry. The store push button switch 95 is a conventional four-pole double throw momentary switch which in the normally closed position grounds the clock inputs to the storage modules. When the push button of the switch is momentarily pushed the clock lines are removed from ground and go to a logic 1 condition allowing the frequency to which the radio is tuned to be stored and displayed by the readout indicators until the button is again actuated and the clock lines go high" to accept a new frequency. The circuit isolation of each storage module in the store push button is not necessary with some solid state storage modules. Those skilled in the art in practicing this invention will readily understand from the known characteristics of the particular modules being utilized whether the individual modules may be connected together so as to use a single pole switch instead of the isolation afforded by the use of an independent pole for each module. Unlike the previously mentioned electromechanical indicator which takes an appreciable amount of time to change indications, the solid state devices, for practical purposes, change almost instantaneously. Due to this fact response time of the solid state devices it has been found that the time required to manually push the store button 95 down and release it is sufficient time for the LED indicators to completely change and thus no additional time delay circuit has been necessary as was needed with the electromechanical indicators.

Each of the foregoing particularly enumerated display characters has a LED decimal point indicator such as 96 associated with the character. In this particular embodiment of the invention when used with a 1,750 channel AN/ARC-34 communication set the LED 96 of the last digit may be used or a mechanical indication (such as a paint spot) may be used to indicate the decimal point.

it is to be understood that while embodiments of this invention have been described in detail for the 1,750 band AN/ARC-34 set it is equally applicable to the 3500 band AN/ARC-34 set by adding another digit indicator to the right of the decimal point indicating either a 0 or 5. For example 235.70 megahertz or 235.75 megahertz. Also the invention may readily be used with communication sets operating in the UHF spectrum having six-digit indicators and with communications sets operating in the VHF spectrum (these normally tune between 116.000 megahertz and 149.975 megahertz.)

While the primary utility of the invention is considered to be for aircraft it may be utilized equally well in ground installations such as control towers, emergency communication sets and other Shore and ship installations.

We claim:

1. In a radio communication set having a plurality of selectable tuned frequencies with each selected tuned frequency represented by a coded electrical output signal, and a slaved electromechanical display indicator, cooperating by electrical cable connection with the said coded electrical output signals of the said communication set, indicating the selected tuned frequency, the said slaved indicator having a maximum response time of approximately one second, a motor drive cable connection, and cable ground connection, the improvement for converting the said slaved indicator to a store and recall indicator, comprising:

a. a manually actuated momentary push button electrical switch;

b. a relay having a normally open contact;

c. An electronic circuit having an RC time constant cooperating with the said electrical cable responsive to the said momentary push button switch for actuating said relay to close the said normally open relay contact for approximately 1.2 seconds with each actuation of the said push button; and

(1. means for connecting in series relationship the said normally open relay contact with the motor drive cable connection of the said slaved electromechanical display indicator and the said electrical cable. 

1. In a radio communication set having a plurality of selectable tuned frequencies with each selected tuned frequency represented by a coded electrical output signal, and a slaved electromechanical display indicator, cooperating by electrical cable connection with the said coded electrical output signals of the said communication set, indicating the selected tuned frequency, the said slaved indicator having a maximum response time of approximately one second, a motor drive cable connection, and cable ground connection, the improvement for converting the said slaved indicator to a store and recall indicator, comprising: a. a manually actuated momentary push button electrical switch; b. a relay having a normally open contact; c. An electronic circuit having an RC time constant cooperating with the said electrical cable responsive to the said momentary push button switch for actuating said relay to close the said normally open relay contact for approximately 1.2 seconds with each actuation of the said push button; and d. means for connecting in series relationship the said normally open relay contact with the motor drive cable connection of the said slaved electro-mechanical display indicator and the said electrical cable. 